The DC-DC converter has been commercialized and widely used in UPS systems, battery charge and discharge devices, electric vehicles, starter/generator systems, aeronautics and space power systems, remote and data communication systems, computer equipment, office automation equipment, industrial instruments and meters, and other occasions. Varying with the operating mode, DC-DC converters can be divided into topological structures such as step-down, step-up, step-down/step-up, flyback, forward, half-bridge, full-bridge, push-pull, etc. With increasing requirement for the switching power supply performance, it is necessary to develop a new circuit topological structure to implement a high-efficiency DC-DC converter.
Due to the advantages such as low cost and wide range of input voltage, an active-clamped flyback DC-DC converter is usually applied in the “Super Charger” included in the UPS system for charging the external battery. The topological structure of the active-clamped flyback DC-DC converter in the prior art is for example shown in FIG. 1. The disadvantage of such converter topology rests with difficulty to meet the requirement of high efficiency (for example, an efficiency of above 94%).
For the need to improve the efficiency of the converter, Patent Document 1 (CN 101692595 A) proposes a forward-flyback DC-DC converter topological structure, which is shown in the schematic diagram of FIG. 2.
In order to implement the high-efficiency DC-DC converter at low cost, there is still room for further improving the circuit topological structure.